System and method for in vitro analysis of therapeutic agents

ABSTRACT

A system and method for in vitro analysis of therapeutic agents comprising a reservoir adapted to hold a therapeutic agent, a first flow cell having a first cell chamber adapted to receive at least a first sample of the therapeutic agent, a second flow cell having a second cell chamber adapted to receive at least a second sample of the therapeutic agent, the first flow cell having a first path length (b e ′) and the second flow cell having a second path length (b e ″), the first path length being substantially equal to a sensitivity factor (f)×b e ″, a membrane chamber having a biological cell membrane therein adapted to receive at least a third sample of the therapeutic agent, the membrane chamber being further adapted to detect the membrane potential of the biological cell membrane; and spectroscopic detection means for detecting the spectral characteristics of the first and second therapeutic agent samples.

FIELD OF THE PRESENT INVENTION

[0001] The present invention relates generally to electrophysiologicassessment of therapeutic agents. More particularly, the inventionrelates to a system and method for in vitro assessment of therapeuticagents that employs spectroscopic means for accurate determination ofthe agent's concentration.

BACKGROUND OF THE INVENTION

[0002] The potential of cardiovascular and non-cardiovasculartherapeutic agents or drugs to cause prolongation of the QT (i.e.,cardiac repolarization time between two ventricular sequences) intervalof the electrocardiogram has been, and continues to be, a significantfactor in the development of new therapeutic agents. Indeed, it is wellestablished that a wide range of non-cardiovascular therapeutic agentsthat are not expected on the basis of their mechanism of action toprolong QT can produce a substantial number of serious cardiac events.Such agents belong to different pharmacological classes, such aspsychotropic drugs (e.g., tricyclic-amitriptiline and tetracyclicantidepressants, phenothiazine derivatives, haloperidol, pimozide,risperidone and sertindole), prokinetic (e.g., cisapride), antimalarialmedicines (e.g., halofantrine, quinine, and chloroquine), antibioticsbelonging to several chemical classes (e.g., azithromycin, erythromycin,clarithromycin, spiramycin, pentamidine, trimethoprim-sulfamethoxazoleand sparfloxacin), antifungal agents (e.g., ketoconazole, fuconazole anditraconazole), agents for treating urinary incontinence (e.g.,terodiline), and certain histamine H₁-receptor antagonist (e.g.,astemizole, terfenadine and diphenhydramine).

[0003] These therapeutic agents, in certain very rare instances, cantrigger life-threatening polymorphic ventricular tachycardias, such astorsade de pointes, often in the presence of additional factorsfavoring, directly or indirectly, proarrhythmic events. The relevantfactors include congenital or acquired long-QT syndrome, ischemic heartdisease, congestive heart failure, severe hepatic or renal dysfunction,bradycardia, electrolyte imbalance (e.g., hypokalemia due to diuretictreatment, hypomagnesemia, hypocalcemia, acidosis and intracellular Ca⁺⁺loading), intentional or accidental overdose, and concomitant treatmentwith ion channel blocking drugs or agents that inhibit the drugdetoxification processes.

[0004] Several preclinical techniques have thus been employed toevaluate the cardiovascular effects of proposed therapeutic agents. Thenoted techniques to determine concentration of proposed therapeuticagents primarily comprise high performance liquid chromatography (HPLC)or other analytical assays that are generally limited to highertherapeutic agent concentrations unless pre-concentration or largevolumes are employed.

[0005] It is, however, well known that the noted physiologicalanalytical assays are often laborious, expensive, time consuming andfrustrated by technical problems. Further, HPLC and/or assays mayrequire hours to days to analyze samples and process data depending onthe complexity and number of samples.

[0006] It is therefore an object of the present invention to provide asystem and method for high-speed, economical in vitro analyses oftherapeutic agents.

[0007] It is another object of the present invention to provide a systemand method for in vitro analysis of low concentration therapeuticagents.

[0008] It is yet another object of the present invention to provide asystem and method for correlating the electrophysiological effects of aproposed therapeutic agent over a broad concentration range.

SUMMARY OF THE INVENTION

[0009] In accordance with the above objects and those that will bementioned and will become apparent below, in a preferred embodiment, thesystem for in vitro analysis of therapeutic agents in accordance withthis invention comprises a reservoir adapted to hold a therapeuticagent, a first flow cell having a first cell chamber adapted to receiveat least a first sample of the therapeutic agent, a second flow cellhaving a second cell chamber adapted to receive at least a second sampleof the therapeutic agent, the first flow cell having a first path length(b_(e)′) and the second flow cell having a second path length (b_(e)″)the first path length being substantially equal to a sensitivity factor(f)×b_(e)″, a membrane chamber having a biological cell membrane thereinadapted to receive at least a third sample of the therapeutic agent, themembrane chamber being further adapted to detect the membrane potentialof the biological cell membrane, and spectroscopic detection means fordetecting the spectral characteristics of the first and secondtherapeutic agent samples.

[0010] The method for in vitro analysis of therapeutic agents inaccordance with the invention preferably comprises the steps of (i)introducing a first sample of a therapeutic agent into a first flow cellhaving a first path length (b_(e)′), (ii) introducing a second sample ofthe therapeutic agent into a second flow cell having a second pathlength (b_(e)″), the first path length (b_(e)′) being substantiallyequal to a sensitivity factor (f)×b_(e)″, (iii) introducing a thirdsample of the therapeutic agent into membrane chamber means having abiological cell membrane disposed therein, (iv) measuring the absorptionspectrum of the first therapeutic agent sample by transmitting a givenwavelength of a first light into the first flow cell, (v) measuring theabsorption spectrum of the second therapeutic agent sample bytransmitting a given wavelength of a second light into the second flowcell, and (vi) detecting the membrane potential of said biological cellmembrane.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further features and advantages will become apparent from thefollowing and more particular description of the preferred embodimentsof the invention, as illustrated in the accompanying drawings, and inwhich like referenced characters generally refer to the same parts orelements throughout the views, and in which:

[0012]FIG. 1 is a schematic illustration of one embodiment of the invitro spectroscopic system for analysis of therapeutic agents accordingto the invention;

[0013]FIG. 2 is a partial section plan view of one embodiment of a flowcell according to the invention;

[0014]FIG. 3 is a partial section plan view of an additional embodimentof a flow cell according to the invention;

[0015]FIG. 4 is a schematic illustration of a flow cell body showing theattenuated light path according to the invention;

[0016]FIG. 5 is a graphical illustration of absorbance spectra of apharmaceutical composition having a low concentration therapeutic agentand a high concentration therapeutic agent;

[0017]FIG. 6 is a schematic illustration of the spectroscopic meansaccording to the invention; and

[0018]FIG. 7 is a partial section perspective view of the membranechamber means according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] The method and system of the present invention substantiallyreduces or eliminates the drawbacks and shortcomings associated withprior art electrophysiologic assessment of therapeutic agents. Asdiscussed in detail below, the system generally includes a plurality offlow cells, spectroscopic means in communication with the flow cells,membrane chamber means and flow passage means for introducing thesubject therapeutic agent(s) to the flow cells and membrane chambermeans.

[0020] By the term “therapeutic agent”, as used herein, it is meant tomean and include active ingredients, components or elements of apharmaceutical composition, drugs and medicaments.

[0021] Cardiac action potential (or membrane potential) is generallydefined as the pattern of electrical activity that is associated withexcitable biological cells (e.g., heart cells). It is the result ofnumerous, distinct, successively activated currents generated by thepassage of biologically important ions (Na⁺, Ca⁺⁺ and K⁺) throughspecialized membrane structures such as ionic pumps and exchangers and,most importantly, voltage-gated ion channels. These currents areconsidered to be depolarizing when they carry extracellular positivecharges into the cell and to be repolarizing when they carry positivecharges to the cell exterior.

[0022] Therapeutic agents that modify the normal flux of ions throughchannels can, and in many instances will, modify certain aspects of themembrane potential and, thus, affect cardiac function. Indeed, blockersof Na⁺ channels reduce the rate of rise of the membrane potential (Vmax)and can produce disturbances in cardiac conduction, which, if severe,may be life threatening. Agents that decrease the rate of Na-currentinactivation and increase residual Na-current can prolong the durationof the action potential (ADP), prolong the QT interval and thus maytrigger torsades de pointes arrhythmias. Blockers of Ca⁺⁺ channelsgenerally decrease ADP, reduce the rate of A-V conduction and producecardiac depression, whereas Ca⁺⁺ channel-activators prolong ADP and maycause arrhythmias. Finally, K⁺ channel-blockers prolong ADP and QT andcan provoke arrhythmias, whereas K⁺ channel-activators shorten ADP andcan also trigger arrhythmia.

[0023] Thus, an effective indicator (or parameter) of possible adversecardiac effects of a proposed therapeutic agent is the change inmembrane potential (i.e., membrane resting potential) resulting from theintroduction or exposure to the therapeutic agent. Indeed, the notedparameter is often deferred to in conventional physiological assessmentsof proposed therapeutic agents (or drug candidates). As discussed indetail below, the noted parameter is also employed in the presentinvention to assess the potential physiological effect(s) of atherapeutic agent.

[0024] Referring now to FIG. 1, there is shown a schematic illustrationof one embodiment of the in vitro analysis system 5 of the invention. Asillustrated in FIG. 1, the system 5 preferably includes reservoir means(e.g. reservoir) 10, optic based spectroscopic detection means 20, aplurality of flow cells, preferably first and second flow cells 60, 70,membrane chamber means 40 and flow passage means 12.

[0025] According to the invention, the reservoir means 10 is designedand adapted to store at least one therapeutic agent in diluent. As willbe appreciated by one having ordinary skill in the art, various capacity(and configuration) reservoir means 10 may be employed within the scopeof the invention. In a preferred embodiment of the invention, thecapacity of the reservoir means 10 is in the range of 1 to 2000 ml.

[0026] The reservoir means 10 is further designed and adapted to receivethe flow passage means 12 of the invention, which preferably comprisessubstantially non-adsorbing tubing (e.g., stainless steel, PEEK®. Asillustrated in FIG. 1, pump means 14 is also provided to facilitate flowof the therapeutic agent (i.e., therapeutic agent sample or samples)from the reservoir means 10 to and through the first and second flowcells 60, 70. The pump means 14 is in communication with the flowpassage means 12 and is preferably disposed between the reservoir means10 and the flow cells 60, 70. According to the invention, the pump means14 is capable of achieving a sample flow rate in the range of ≦0.5 to≧10 ml/min., more preferably, in the operating range of approximately 2to 5 ml/min.

[0027] As will be appreciated by one having ordinary skill in the art,various pump means 14 may be employed within the scope of the inventionto provide the noted sample flow rate(s). In a preferred embodiment, thepump means 14 comprises a peristaltic pump.

[0028] Referring now to FIG. 2, there is shown one embodiment the firstflow cell 60 of the invention. For simplicity, only the first flow cell60 will be illustrated and described. However, it is to be understoodthat the second flow cell 70 of the noted embodiment is similarlyconstructed and the description of the first flow cell 60 is equallyapplicable to each flow cell 60, 70.

[0029] As illustrated in FIG. 2, the flow cell 60 preferably includes asubstantially tubular body 62 having an inlet port 64, an outlet port 66and a cell chamber, designated generally 63, disposed therein that isadapted to receive a therapeutic agent sample. According to theinvention, the inlet and outlet ports 64, 66 and cell chamber 63 definea flow passage 61.

[0030] As will be appreciated by one having ordinary skill in the art,various flow cell body 62 materials may be employed within the scope ofthe invention. In a preferred embodiment of the invention, the body 62of each flow cell 60, 70 includes a core comprising a polymer, silica,chalcogenide or other like materials and cladding 67 disposed on theouter surface of the core comprising a polymer or doped silica or otherlike materials (see FIGS. 2 and 4).

[0031] According to the invention, the first flow cell 60 furtherincludes first light transmission means 21 a adapted to provide a givenwavelength of excitation light or radiation (and/or a given rangethereof) to the flowable therapeutic agent present in the first flowcell chamber 63 (i.e., first sample) and first light detection means 23a for detecting the transmitted light from the first sample. The secondflow cell 70 similarly includes second light transmission means 21 badapted to provide a given wavelength of excitation light (and/or agiven range thereof) to the sample present in the cell chamber of thesecond flow cell 70 (i.e., second sample) and second light detectionmeans 23 b for detecting the transmitted light from the second sample.

[0032] Referring now to FIG. 3, there is shown another embodiment of aflow cell 80 of the invention. The flow cell 80 similarly includes aninlet port 82, an outlet port 84 and a cell chamber, designatedgenerally 86, disposed there between that is similarly adapted toreceive a therapeutic agent sample.

[0033] The flow cell 80 further includes first light transmission means85 adapted to provide a given wavelength of excitation light orradiation to the flowable therapeutic agent present in the flow cellchamber 86 (i.e., first sample) and first light detection means 87 fordetecting the transmitted light from the first sample.

[0034] It is well known that when each sample passes through arespective flow cell chamber (e.g., 63) the amount of excitation lighttransmitted into and through the cell chamber 63 decreases in accordancewith Beer's Law, i.e., $\begin{matrix}{A = {\frac{I}{I_{o}} = 10^{- {\propto {b\quad c}}}}} & {{Eq}.\quad 1}\end{matrix}$

[0035] where:

[0036] A=absorbance;

[0037] I=power of transmitted radiation;

[0038] I_(o)=power of incident radiation;

[0039] c=molar absorptivity of the sample;

[0040] c=sample concentration (moles/liter); and

[0041] b=path length of the light in the chamber (cm.)

[0042] The absorbance (A) is thus defined as the product of ∝bc.According to Beer's Law, absorbance (A) is also proportional to both thesample concentration (c) and path length (b).

[0043] As will be appreciated by one having ordinary skill in the art,the path length (b) is generally deemed a “straight path length” that isapplicable in light transmission/detection configurations such as thatillustrated in FIG. 3. It will further be appreciated by one havingskill in the art that the noted Beer's Law relationship is similarlyapplicable for the light transmission/detection configuration (i.e., 21a, 23 a) of the cylindrical flow cell 60 of the invention (see FIG. 2),which employs attenuated total reflection.

[0044] Referring to FIG. 4, it is well known that when radiation (orlight), designated generally 100, undergoes total internal reflection102, it actually penetrates a fraction of a wavelength into the medium(or sample) beyond the reflecting surface. The penetration depth isgenerally denoted d_(p).

[0045] Since the penetration depth d_(p) is defined as a unitlength/reflection, an equivalent path length (b_(e)) can thus be derivedas follows:

b _(e) =d _(p) ×R×L  Eq.2

[0046] where:

[0047] d_(p)=penetration depth per reflection;

[0048] R=number of reflections per unit length; and

[0049] L=length of tube or cell.

[0050] The equivalent path length (b_(e)) can then be employed in Eq.1to derive the absorbance of a respective sample (A).

[0051] As will further be appreciated by one having ordinary skill inthe art, the effective path length (b_(e)) of a respective flow cell 60,70 is directly dependent on the length of the flow cell body 62. Thus,the length of each flow cell 60, 70 can be tailored to provide differentpath lengths.

[0052] It can further be deduced from Beer's Law that if the absorbancerange of the spectroscopic means (e.g., spectrophotometer) is fixed,which is a common element of conventional spectroscopic means, the pathlength (b or b_(e)) must be increased for lower molar absorptivity (∝)or lower concentration (c). However, as is well known in the art, theresponse band generally associated with a larger path length isundesirably narrow and, hence, limited.

[0053] It is also well known in the art that a broader response band canbe achieved by employing two (2) flow cells having different pathlengths (b_(e)′, b_(e)″). The typical path lengths generally range from0.1 to 100 cm.

[0054] Applicants have however found that an optimum dynamic (i.e.,substantially linear) response range can be achieved if b_(e)′ issubstantially equal to b_(e)″ ×a sensitivity factor (f). According tothe invention, the sensitivity factor (f) preferably has a value in therange of 1 to 100. More preferably, f has a value in the range of 1 to20.

[0055] Referring to FIG. 5, there are shown absorbance spectra of a lowconcentration therapeutic agent (i.e., ˜18 ng/ml) and a highconcentration therapeutic agent (i.e., ˜3800 ng/ml). The notedabsorbance spectra was derived with a first flow cell having a pathlength of approx. 5 cm and a second flow cell having a path cell ofapprox. 50 cm (i.e., f=10).

[0056] Referring to Curve A, it can be seen that a path length of 5 cmwas insufficient to detect the low concentration therapeutic agent overa range of wavelengths from 200 nm to 400 nm. However, as illustrated byCurve B, the same agent was readily detectable (and quantifiable) at apath length of 50 cm.

[0057] Referring now to Curve C, it can be seen that the highconcentration therapeutic agent was not quantifiable at a path length of50 cm. However, as illustrated in Curve D, the same agent was readilydetectable at a path length of 5 cm.

[0058] Accordingly, in a preferred embodiment of the invention, thefirst flow cell 60 has an effective path length (b_(e)′) in the range of0.1 to 100 cm and second flow cell 70 has an effective path length(b_(e)″) in the range of 0.1 to 100 cm. More preferably, the first flowcell 60 has an effective path length (b_(e)′) in the range of approx. 5to 50 cm and the second flow cell 70 has a path length (b_(e)″) in therange of approx. 50 to 100 cm. Applicants have found that accuratespectral characteristics of therapeutic agents having a substantiallylow concentration in the range of 5 to 10 ng/ml can readily be detectedby virtue of the noted range of path lengths (b_(e)′ b_(e)″).

[0059] Referring now to FIG. 6, in addition to the first and secondlight transmission means 21 a, 21 b and first and second light detectionmeans 23 a, 23 b shown in FIG. 2, the spectroscopic means 20 of theinvention further includes light source means 22 for providing thedesired wavelength of light to the first and second light transmissionmeans 21 a, 21 b via optical lines 24 a and 24 b, respectively, andanalyzer means 26 for analyzing the light detected by the first andsecond light detection means 23 a, 23 b, which is communicated to theanalyzer means 26 via optical lines 28 a and 28 b, respectively.

[0060] In additional envisioned embodiments of the invention, thereservoir means 10 also includes light transmission means 25 a and lightdetection means 25 b that are operatively connected to the spectroscopicmeans 20 of the invention via optical lines 27 a, 27 b. As will beappreciated by one having ordinary skill in the art, the reservoir meanslight transmission and detection means 25 a, 25 b provides means forsimultaneously assessing and monitoring the agent contained in thereservoir means 10 and, hence, means for detecting therapeutic agentloss and ensuring that the samples analyzed in the flow cells 60, 70 arerepresentative of the source therapeutic agent contained in thereservoir means 10.

[0061] As illustrated in FIG. 6, the spectroscopic means 20 furtherpreferably includes memory means 30 for storing at least the detectedspectroscopic characteristics of the first and second samples (andsource agent contained in the reservoir means 10) and the controlparameters for the spectroscopic means of the invention, processor means32 for processing at least the spectroscopic characteristics of thesamples (and source agent) and first display means 34 (shown in phantom)for displaying at least the spectroscopic characteristics of thesamples, the source pharmaceutical agent contained in the reservoirmeans 10 and the “processed” spectroscopic characteristics of thesamples (e.g., mean values).

[0062] As will be appreciated by one having ordinary skill in the art,various conventional light source means 22 and/or analyzer means 26 canbe employed within the scope of the invention to provide a given rangeof wavelength of light, analyze the spectroscopic characteristics (e.g.,absorption spectrum of the absorbed light) acquired by the first andsecond light detection means 23 a, 23 b and control the spectroscopicmeans 20 of the invention, such as the analyzers disclosed in U.S. Pat.No. 4,664,522 and the MCS-521 fiber optic UV/VIS spectrophotometerdistributed by Carl Zeiss, which are incorporated by reference herein.The analyzer means 26 and/or the processor means 32 may also comprise apersonal computer.

[0063] Referring now to FIG. 7, there is shown the membrane chambermeans 40 of the invention. The membrane chamber means 40 includes amembrane chamber body 42 having a perfusion inlet 44, a perfusion outlet46, a preparation well 48, a membrane well 50 and a diffuser plate 52disposed between the preparation well 48 and membrane well 50.

[0064] As illustrated in FIG. 7, the membrane chamber means 40 furtherincludes membrane means 52 disposed in the membrane well 50. By the term“membrane means”, as used herein, it is meant to mean a biological cellmembrane, including a sheet or layer of a biological organ, theventricular muscle and/or papillary muscle, and Purkinje fibers.

[0065] In a preferred embodiment of the invention, the membrane means 52comprises a Purkinje fiber. As is well known in the art, Purkinje fibersare often employed in electrophysiological assessments because it isbelieved that the major ionic currents underlying their actionpotentials resemble those contributing to the repolarization process ofthe human heart.

[0066] To assess the membrane potential of the membrane means 52, themembrane chamber means 40 further includes a plurality of electrodes.Referring to FIG. 7, at least one, preferably two, bipolar electrodes 54a, 54 b are operatively connected to the membrane means 52 proximate oneend thereof. The electrodes 54 a, 54 b are also in communication withthe stimulation means 55 of the invention via leads 54 a, 54 b (seeFIG. 1) and are adapted to provide a stimulating charge or current tothe membrane means 52.

[0067] As illustrated in FIG. 7, a further electrode is also provided.In a preferred embodiment, the noted electrode comprises anintracellular microelectrode 56 that is also operatively connected tothe membrane means 52.

[0068] According to the invention, the microelectrode 56 is designed andadapted to detect the membrane potential of the membrane means 52. Themicroelectrode 56 is preferably in communication with second displaymeans 58 (via lead 57 c) that is adapted to provide a visual display orindication of the detected potential (see FIG. 1).

[0069] Assessment of therapeutic agents in accordance with the presentinvention is preferably accomplished as follows: The spectroscopic meansof the invention is initially calibrated by conventional means. Suchmeans includes analysis of blank (or primary) samples as a UV referenceand an analysis of calibration samples with respective blank samples asa reference.

[0070] After calibration of the spectroscopic means 20, flow of thetherapeutic agent (preferably, in diluent) is initiated and thetherapeutic agent is introduced into and through the flow passage means12 via pump means 14. The therapeutic agent is then introduced into andthrough the flow passage 61 of the first and second flow cells 60, 70,which are preferably connected in series, and the membrane chamber means40.

[0071] The spectroscopic characteristics of the therapeutic agentpresent in the first flow cell 60 (i.e., first sample) and the secondflow cell 70 (i.e., second sample) are then detected (preferably,substantially simultaneously) by the above described spectroscopic means20 of the invention. The spectroscopic characteristics are thenprocessed and analyzed by conventional means.

[0072] In a preferred embodiment, substantially simultaneously with thespectroscopic analysis and while the therapeutic agent is present in themembrane well 50 of the membrane chamber means 40 (i.e., third sample),the membrane means 52 is subjected to an initial current via stimulatingelectrodes 54 a, 54 b. The membrane potential is then detected viaelectrode 56 that is displayed on the second display means 58 of theinvention. The change in membrane potential is then readily determinedby comparing the detected membrane potential to the potential of themembrane means 52 prior to exposure to the therapeutic agent.

[0073] As will be appreciated by one having ordinary skill in the art,the system and method of the invention, described in detail above, isalso applicable to analyses of pharmaceutical compositions containing atherapeutic agent and, in particular, pharmaceutical compositions havinga substantially low concentration of therapeutic agents.

Summary

[0074] From the foregoing, one of ordinary skill in the art can easilyascertain that the present invention provides the following advantages:

[0075] 1. High speed, highly accurate and economical (i.e., low cost) invitro analyses of therapeutic agents.

[0076] 2. High speed, efficient in vitro analyses of pharmaceuticalcompositions having a substantially low concentration (i.e., 5-10 ng/ml)of therapeutic agents.

[0077] 3. High speed, efficient means for correlating theelectrophysiological effects of a proposed therapeutic agent over abroad concentration range.

[0078] 4. Means for assessing and monitoring the stability of thetherapeutic agent during in vitro analyses.

[0079] 5. Means for assessing and monitoring agent loss (e.g., glasswareabsorption and/or attachment) during in vitro analyses.

[0080] 6. Means for rapidly and efficiently detecting carryover (i.e.,cross-contamination) in a reservoir and/or feed lines.

[0081] Without departing from the spirit and scope of this invention,one of ordinary skill can make various changes and modifications to theinvention to adapt it to various usages and conditions. As such, thesechanges and modifications are properly, equitably, and intended to be,within the full range of equivalence of the following claims.

What is claimed is:
 1. A system for use in in-vitro analysis of atherapeutic agent, said system comprising: a reservoir adapted to holdsaid therapeutic agent; a first flow cell in communication with saidreservoir having a first cell chamber adapted to receive at least afirst sample of said therapeutic agent; a second flow cell incommunication with said reservoir having a second cell chamber adaptedto receive at least a second sample of said therapeutic agent; saidfirst flow cell having a first path length (b_(e)′) and said second flowcell having a second path length (b_(e)″), said first path length beingsubstantially equal to sensitivity factor (f)×b_(e)″; a membrane chamberin communication with said reservoir having a biological cell membranetherein, said membrane chamber being adapted to receive at least a thirdsample of said therapeutic agent, said membrane chamber being furtheradapted to detect the membrane potential of said biological cellmembrane; and spectroscopic detection means for detecting the spectralcharacteristics of said first and second therapeutic agent samples. 2.The system of claim 1, wherein said spectroscopic detection meansincludes first light transmission means for transmitting a first lightof a given wavelength into said first cell chamber, first lightdetection means for detecting a first transmitted light from said firsttherapeutic agent sample, second light transmission means fortransmitting a second light of a given wavelength into said second cellchamber and second light detection means for detecting a secondtransmitted light from said second therapeutic agent sample.
 3. Thesystem of claim 2, wherein said spectroscopic detection means furtherincludes control means in communication with said first and second lighttransmission means and said first and second light detection means forproviding said first and second lights and analyzing said first andsecond transmitted lights.
 4. The system of claim 1, wherein saidsensitivity factor has a value in the range of 1 to
 100. 5. The systemof claim 4, wherein said sensitivity factor has a value in the range of1 to
 20. 6. The system of claim 1, wherein said first and second pathlengths are in the range of 0.1 to 100 cm.
 7. The system of claim 6,wherein said first path length is in the range of 5 to 50 cm.
 8. Thesystem of claim 6, wherein said second path length is in the range of 50to 100 cm.
 9. The system of claim 1, wherein said spectroscopicdetection means includes third light transmission means for transmittinga third light of a given wavelength into said reservoir and third lightdetection means for detecting a third transmitted light from saidtherapeutic agent contained in said reservoir, said third lighttransmission means and third detection means being in communication withsaid control means.
 10. The system of claim 1, wherein saidspectroscopic means includes first display means for displaying at leastthe spectroscopic characteristics of said first and second therapeuticagent samples.
 11. The system of claim 1, wherein said membrane chambermeans includes second display means for displaying said membranepotential of said biological cell membrane.
 12. A system for use inin-vitro analysis of a therapeutic agent, said system comprising: areservoir adapted to receive said therapeutic agent; a first flow cellin communication with said reservoir having a first cell chamber adaptedto receive a first sample of said therapeutic agent, said first flowcell having an effective path length in the range of approximately 5-50cm; a second flow cell in communication with said reservoir having asecond cell chamber adapted to receive a second sample of saidtherapeutic agent, said second flow cell having an effective path lengthin the range of approximately 50-100 cm; a membrane chamber incommunication with said reservoir having a biological cell membranetherein, said membrane chamber being adapted to receive a third sampleof said therapeutic agent, said membrane chamber being further adaptedto detect the membrane potential of said biological cell membrane; andspectroscopic detection means for detecting the spectral characteristicsof said first and second therapeutic agent samples.
 13. The system ofclaim 12, wherein said spectroscopic detection means includes firstlight transmission means for transmitting a first light of a givenwavelength into said first cell chamber, first light detection means fordetecting a first transmitted light from said first therapeutic agentsample, second light transmission means for transmitting a second lightof a given wavelength into said second cell chamber and second lightdetection means for detecting a second transmitted light from saidsecond therapeutic agent sample.
 14. The system of claim 13, whereinsaid spectroscopic detection means further includes control means incommunication with said first and second light transmission means andsaid first and second light detection means for providing said first andsecond lights and analyzing said first and second transmitted lights.15. The system of claim 14, wherein said spectroscopic detection meansincludes third light transmission means for transmitting a third lightof a given wavelength into said reservoir and third light detectionmeans for detecting a third transmitted light from said therapeuticagent contained in said reservoir, said third light transmission meansand third detection means being in communication with said controlmeans.
 16. The system of claim 15, wherein said spectroscopic meansincludes display means for displaying at least the spectroscopiccharacteristics of said therapeutic agent contained in said reservoirand said first and second therapeutic agent samples.
 17. A method forin-vitro analysis of therapeutic agents, said method comprising thesteps of: introducing at least a first sample of a therapeutic agentinto a first flow cell, said first flow cell having a first path length(b_(e)′); introducing at least a second sample of said therapeutic agentinto a second flow cell, said second flow cell having a second pathlength (b_(e)″); said first path length (b_(e)′) being substantiallyequal to a sensitivity factor (f)×b_(e)″; introducing at least a thirdsample of said therapeutic agent into membrane chamber means having abiological cell membrane disposed therein; measuring the absorptionspectrum of said first therapeutic agent sample by transmitting a givenwavelength of a first light into said first flow cell; measuring theabsorption spectrum of said second therapeutic agent sample bytransmitting a given wavelength of a second light into said second flowcell; and detecting the membrane potential of said biological cellmembrane.
 18. The method of claim 17, wherein said first therapeuticagent sample absorption spectrum and said second therapeutic agentsample absorption spectrum are measured substantially simultaneously.19. The method of claim 17, wherein said sensitivity factor has a valuein the range of 1 to
 100. 20. The method of claim 17, wherein saidsensitivity factor has a value in the range of 1 to
 20. 21. The methodof claim 17, wherein said first and second path lengths are in the rangeof 0.1 to
 100. 22. The system of claim 21, wherein said first pathlength is in the range of 5 to 50 cm.
 23. The system of claim 21,wherein said second path length is in the range of 50 to 100 cm.